I have been doing a restore of a black knight. I have everything completed and reassembled the pin and the bottom two flipper coils lock on. This did not happen before stripping down the playfield. All coils worked fine. I did not remove the driver board, MPU board, or voltage regulator board. They were all working properly and did not need repair. I checked for shorts under the playfield and the flipper switches. Everything looks okay. Diodes on the coils are also okay.

Maybe the driver board? Seems odd since I did not remove it.

Checked q13 on driver board with multimeter and got a bad reading. Anything else I should checke?

Replace q13 coils are still locked on. Didn't notice before but drop target coils on top playfield also locked on.

Thanks as always to helpful Pinsiders.

There are to be a short somewhere then. I edited my post to indicate drop targets on top left playfield also locking on.

I think I am brain dead today.

I have continuity from the cabinet switch wires to the end of the molex connector that connects to back box. If I disconnect the molex connector the two lower flippers and top left drop targets lock on. If I am thinking correctly, the short must then be between the back box and the coils??? If I disconnect all of the solenoid connectors on the driver board the same coils still lock on. If I remove the fuses underneath the playfield the coils still lock on. The only way I can stop the coils from locking on is to disconnect J3 on the power supply.

I have been checking continuity. I have continuity from the top to bottom playfield connector plugs and the lower playfield flippers.

I decided to disconnect everything from the backbox boards except for the voltage regulator board. When powered on the bottom left flipper locks on - right flipper and top left bank targets do not lock on.

Nothing smoked so I am hoping they are not reversed but will double check.

The coil fuse on the playfield or the voltage regulator? If I remove the fuses on the playfield the coils still lock on.

So something is definitely fried. Removed the fuse for the flippers and the MPU board reads 0 with both leds lit. Best I can tell is that something on the board is toast and has locked it up. No displays working. Damn - worked like heck to get this ready to go and it was working fine prior to me stripping the board, etc. Closed the coin door and get the same reading.

Is this repairable? I have read that it is probably IC19 that has failed and maybe IC12 and IC7.

Thanks

Yes, it was the connectors. I had them plugged in to the wrong connector. Nothing smoked, but it was definitely causing the coils to lock on.

Thanks. Really pisses me off. Spent a lot of time on this restore - looks great - but my faulty. I should have checked that the wires matched. Does anyone do system board repairs? I email barakandl to see if he still worked on them.

Thanks for all of the help. Bit the bullet and bought a replacement board. Maybe I will work on my soldering and unsoldering skills and try to repair the MPU and driver board.